Freeing memory

Hi Nigel,

I've updated to current git in the hope the memory freeing problems 
would be solved. Unfortunately, they are still there and I've been 
trying to narrow the issue down. Actually, there are two issues:

First, the memory eating process seems to lock up the machine when it 
requests too much memory. Commmit 
f8262d476823a7ea1eb497ff9676d1eab2393c75 "PM / Hibernate: fix the number 
of pages used for hibernate/thaw buffering" doesn't help with that. 
Maybe tuxonice needs to play catch up on that? Using smaller values and 
more tries seems to help with the freezes, but I don't know what a safe 
value would be.

Next, there seems to be a limit to what amount of the pagecache is 
freeable using the tuxonice memory eater method. Having a total of 16 
GiB, I increased the max tries and set a limit of max 4096MiB to free 
per try so that it would not freeze, but the memory eater hit some limit 
(at that time 4973MiB) where it could not free more memory. Dropping the 
caches manually via "echo 1 > /proc/sys/vm/drop_caches" immediately 
solved the problem and resulted in an image of 2180MiB, IIRC 
image_size_limit was set to 3GiB.

There is an easy way to reproduce this, probably both issues actually: 
Just copy some big files, e.g. videos, before hibernating.

I've also used the shrink_all_memory call instead of the separate 
requests for freeing low and high pages, but that didn't make any 
noticable difference. BTW: That debug message in 
tuxonice_prepare_image.c "Asked shrink_all_memory for ... low pages & 
... pages from anywhere) is a bit outdated, since shrink_all_memory is 
no longer used.

I believe that memory freeing seemed to work fine before and the culprit 
is some commit between 3.2-rc6 and 3.3. Might it have to do something 
with what f8262d476823a7ea1eb497ff9676d1eab2393c75 tried to fix? 
However, my machines are all 64 bit. Do you have any idea, shall I try 
to bisect?

Harald

-- 
`Experience is the best teacher.'